what will happen?? well if you say yes...or allow it, then Google will receive your location. Your browser will send your locale info to Google. But unless you have a GPS, and your browser uses it, then Google won't know exactly where you are...just approximately. For instance, I allowed Google to have my locale for Google Maps. But all it can tell, for me at least, is about which half of the state I live in. So for me at least, it's not very close. But it depends on whether you are comfortable with Google knowing where you live (give or take 500 miles) or...you would rather Google not know.

The My Location feature allows Toolbar to determine your approximate location based on your local network information, including details about nearby WiFi access points and/or the nearest router connected to your computer, and share that location with websites you choose. Websites that want to access your location must ask your permission, which you can grant or deny.

* If you enable the My Location feature by granting a website permission to access location, Toolbar will periodically query Google for your current location. In order to determine your location, Toolbar will send Google the hardware IDs (i.e., MAC addresses) and SSIDs of WiFi access points visible to your machine, the hardware ID (i.e., MAC address) of the nearest connected router, and the signal strengths of nearby access points. If you disable the My Location feature, this information will cease to be sent.
* The URLs or other information about websites with which you share your location are not sent to Google by the My Location feature. (Note: if you have also enabled enhanced features, as described below, the URLs may be independently sent by those features). You can always manage the list of websites that have access to your location through Toolbar's Options menu. Third party websites with whom you choose to share your location information are not covered by Google's Privacy Policies.